1. Field of the Invention
The invention relates generally to the field of battery-powered computers. More particularly, the invention relates to using residual energy in battery-powered computers to perform a function before the battery discharges to its cutoff voltage.
2. Discussion of the Related Art
Many conventional battery-powered computers provide only a single warning message before the primary battery discharges to the cutoff voltage and the battery-powered computer can no longer be powered by the primary battery, or a lockout of applications occurs. The user expects to be able to perform one or more pre-cutoff functions to ensure that data stored in the battery-powered computer is not lost when the battery discharges to the cutoff voltage. Similarly, the user expects to be able to execute certain applications after the warning before the applications are locked out.
The single warning message is typically triggered by the operating voltage of the primary battery discharging below a certain predetermined warning voltage. Such operating voltage based warning messages can fail to meet user expectations when, due to accuracy limitations of the voltage detection component(s) used to monitor the operating voltage, the message is provided too late for the user to perform the desired pre-cutoff function, or execute the pre-lockout application. Therefore, what is needed is a warning message that meets user expectations by ensuring that the user can perform the pre-cutoff functions before the battery discharges to the cutoff voltage and can execute certain applications before the applications are locked out.
Another problem with the prior art is that conventional battery-powered computers rely on an alternative energy source to ensure retention of data when the energy level of the primary energy source goes below a minimum energy level for continued normal functioning of the computer. These alternative energy sources can include small batteries such as watch batteries, large capacitors, and other energy storage devices. The capacity requirements for the alternative energy sources are typically much lower than the primary energy source capacity.
For some conventional battery-powered computers, the alternative energy source provides a voltage source when the batteries are replaced. For example, for Palm III(trademark) computers, a capacitor is charged by the primary energy source (two AAA alkaline batteries). The capacitor provides an alternative energy capacity that enables the Palm III to retain data for approximately one minute to three minutes with no charge from the alkaline batteries, e.g., when low charge alkaline batteries are replaced by the user.
A problem with this technology has been that the alternative energy source does not provide enough time for replacement of the primary energy source when the user cannot provide replacement batteries within the proscribed time (e.g., one to three minutes), and data stored in the battery powered computer is therefore lost. Therefore, what is required is a solution that uses the primary energy source to provide sufficient time for data retention during a period of time when the primary energy source is susceptible to discharging to the cutoff voltage or is otherwise unable, in the absence of the solution, to ensure that the data will be retained.
One unsatisfactory approach, in an attempt to solve the above-discussed problems, involves the use of secondary or alternate watch batteries in certain handheld connected organizers that use the Windows(copyright) CE operating system. Unless the remaining capacity of the alternate battery is monitored, the alternate battery is subject to unpredictable failure just at the time it is needed most. But, monitoring the remaining capacity of the alternate battery is duplicative of any provision to monitor the capacity of the primary battery and is therefore inefficient.
Methods and apparatus for determining residual battery voltage are provided by U.S. Pat. No. 5,784,295, issued to Hinohara on Jul. 21, 1998. However, these methods and apparatus do not ensure that sufficient time for data retention is provided.
Several laptop computers provide a warning that the main battery needs to be recharged and then place the computer into a sleep mode. The remaining charge of the main battery is then used as a capacitor to retain the data in the memory. The warnings provided by these computers can be too late for the user to complete desired tasks before cutoff because the warnings are based on the operating voltage of the primary energy source, which is subject to inaccurate voltage measurement.
Heretofore, the requirement of using the capacity of the primary battery to ensure that data stored in the computer is retained has not been fully met. What is needed is a solution that addresses this requirement.
A primary goal of the invention is to reserve a residual battery capacity in a primary energy source of a battery-powered computer for one or more pre-cutoff functions. One example of a pre-cutoff function is using the residual battery capacity to retain data stored in the computer between charging opportunities.
Another goal is to provide a warning message that is based on a measurement of time from when a signal is received by the processor disposed in the computer. The time-based warning avoids voltage measurement accuracy limitations that are characteristic of analog to digital converters and can detrimentally affect the timing of warning messages based on operating voltage measurements.
In accordance with these goals, there is a particular need for a method including a hardware lockout of power and application interrupt signals when the battery capacity has decreased to within a predetermined amount above the cutoff voltage, and a method for providing a time-based warning. The methods and apparatus according to the invention provide advantages because they provide time-based warnings and hardware lockouts that enable the battery-powered computer to use the residual energy in the rechargeable battery to perform pre-cutoff functions such as ensuring that data stored in the computer is retained in between opportunities to charge the battery.
A first and a second aspect of the invention are implemented in various embodiments based on a battery-powered computer including a primary energy source. The primary energy source for operation of the battery-powered computer includes at least one battery and can be a rechargeable battery. In some embodiments the rechargeable battery can be the sole energy source for operation of the battery-powered computer. In other embodiments, a secondary source of energy can be provided to ensure that the data is retained in the memory even after the residual energy in the primary energy source has been depleted to approximately the cutoff voltage.
The first aspect of the invention includes a battery-powered computer having a processor and a memory. The memory is coupled with the processor to: calculate a measure of time after a signal is received by the processor, and to provide a time-based warning message based on the measure of time. The warning message indicates that the energy capacity of the battery has discharged to a low level.
The second aspect of the invention includes a battery-powered computer having a battery, a processor and hardware resources coupled to the processor. The battery has an operating voltage, and a cutoff voltage below which no functioning of the battery-powered computer can be executed using the primary energy source. The hardware resources are coupled with the processor to respond to the operating voltage being approximately equal to a hardware lockout voltage by preventing the activation of power and applications in the battery-powered computer. Upon discharging to the hardware lockout voltage, the primary energy source retains a residual energy above the cutoff voltage sufficient for the battery-powered computer to perform at least one function before the primary energy source discharges to the cutoff voltage.
A third aspect of the invention is a method implemented in a battery-powered computer for providing a warning based on at least one measurement of time. The method includes a processor receiving a signal at approximately a first time and starting at least one timer at approximately the first time. The method also includes tracking at least one measure of time from approximately the first time, and the battery-powered computer responding to a first measure of time being approximately equal to a second time by providing a warning that a primary energy source of the battery-powered computer has discharged to a low voltage.
A fourth aspect of the invention is a method for using residual energy in a battery-powered computer. The method includes the primary energy source discharging to approximately a hardware lockout voltage level; and responsive thereto, a processor preventing activation of power and applications in the battery-powered computer. Upon discharging to the hardware lockout voltage, the primary energy source has a residual energy sufficient to perform at least one function within a first duration before the primary energy source discharges to a cutoff voltage.